Is an Investor-State Agreement necessary to pursue trade?

No. Even though Australia does not have an investor-state treaty with China, they lead the globe in Chinese investment.

In 2012, investment from China to Australia stood at $51 billion (US), eclipsing the United States ($50.7 billion) and far surpassing Canada ($36.7 billion).

*Source: KPMG – Demystifying Chinese Investment, August 2012